The present invention relates generally to a bone-adjusting device which can be used to achieve distraction osteogenesis of bone, particularly as used in humans.
The process of distraction osteogenesis has been employed by orthopedic surgeons to reconstruct and lengthen long bones in the lower extremities. This process involves placing a vascularized piece of bone under tension, thereby inducing native bone formation via the creation of a bony reparative callus which is then placed under tension and generates new bone. ["Distraction Osteogenesis for Reconstruction of Mandibular Symphyseal Defects" by Annino et al.] In order to effect distraction osteogenesis, a surgeon generally performs an osteotomy thereby sectioning or segmenting the bone to be altered into more than one piece and as the bone heals, it is slowly and gradually expanded over a period of time so that the blood vessels and nerve ends remain intact during the distraction process. For instance, the bone may be extended a millimeter a day, often by performing two extensions of half a millimeter, for three or four weeks. Often these distractions are performed by adjustments made by the patient's parent or other close relative or friend.
A device sold by Normed is known which can be used to perform linear distraction. This device is composed of two arms, a central assembly which retains bone-pins and two bone-pin clamps which can be adjusted linearly along the length of the two arms and which also retain bone-pins. The housing assembly allows the angular relation between the arms to be reset or reconfigured in a single plane for the particular patient before the device is fixed to the bone-pins. Once the angular configuration of the arms of the device is set for the patient and fixed to the bone-pins, the angular relation between the arms is fixed and the bone-pin clamps are adjusted along the length of the device to effect linear distraction. This device, although allowing for linear distractions, does not allow continuous infinite angular adjustments in order to achieve angular distraction osteogenesis.
A device as described in U.S. Pat. No. 5,160,335 is known which can be used to perform distraction osteogenesis. This device is a pin-holder support which comprises a clamp for gripping the bone-pins, a jaw which positions the device along a fixation bar, a deflection member for adjusting the angular position of the clamp relative to the fixation bar and a blocking means to maintain the device in a desired position. This device only contemplates distraction along a single axis and does not provide for angular distraction.
A device as described in U.S. Pat. No. 3,961,854 is known which can be used to orient and maintain a rod or stem in any direction. It is composed of a U-shaped element on the branches of which a flange closing the U is detachably secured, at least two cylindrical superposed plates, one of which is rotatably engaged in the flange and the other in the U-shaped element, the adjacent surfaces of the plates each having grooves which cooperatively define a hole to receive the rod or stem to be oriented. This device contemplates distraction along a single axis, and it does not provide for angular distraction.
There are obvious problems with these known prior art devices. These devices provide for linear adjustment only and do not provide for gradual, precise and controlled angular adjustment in order to form curved, bent or other intricately-shaped bones through angular distraction osteogenesis. The importance of being able to form curved sections or portions of bone is demonstrated by angular distraction of the mandible which rounds out the patient's bite and properly contours the face. Moreover, these prior devices do not allow three-dimensional distraction osteogenesis wherein both linear and angular adjustments may be made, both independently or simultaneously, along each of two independent axes defining two different planes.